Parts per worksheet 1a-c | Science, Chemistry, Solutions Chemistry ... - Free Printable

Problem Analysis:

We are given a solution where 25 grams of a chemical is dissolved in 75 grams of water. We need to calculate the concentration of the chemical in three different units:
1. Parts per hundred (pph)
2. Parts per thousand (ppt)
3. Percentage by mass (%)

Step-by-Step Solution:

#### Step 1: Total Mass of the Solution
The total mass of the solution is the sum of the mass of the solute (chemical) and the mass of the solvent (water):
\[
\text{Total mass} = \text{Mass of solute} + \text{Mass of solvent}
\]
\[
\text{Total mass} = 25 \, \text{g} + 75 \, \text{g} = 100 \, \text{g}
\]

#### Part (a): Concentration in Parts per Hundred (pph)

Parts per hundred (pph) is defined as:
\[
\text{Concentration (pph)} = \left( \frac{\text{Mass of solute}}{\text{Total mass of solution}} \right) \times 100
\]

Substitute the given values:
\[
\text{Concentration (pph)} = \left( \frac{25}{100} \right) \times 100 = 25 \, \text{pph}
\]

#### Part (b): Concentration in Parts per Thousand (ppt)

Parts per thousand (ppt) is defined as:
\[
\text{Concentration (ppt)} = \left( \frac{\text{Mass of solute}}{\text{Total mass of solution}} \right) \times 1000
\]

Substitute the given values:
\[
\text{Concentration (ppt)} = \left( \frac{25}{100} \right) \times 1000 = 250 \, \text{ppt}
\]

#### Part (c): Percentage by Mass (%)

Percentage by mass (\%) is defined as:
\[
\text{Concentration (\%)} = \left( \frac{\text{Mass of solute}}{\text{Total mass of solution}} \right) \times 100
\]

Substitute the given values:
\[
\text{Concentration (\%)} = \left( \frac{25}{100} \right) \times 100 = 25 \, \%
\]

Final Answers:

\[
\boxed{25 \, \text{pph}, 250 \, \text{ppt}, 25 \, \%}
\]